The present invention relates generally to fiber optics communications and more specifically to parallel optics modules for use in fiber optic communications systems.
The majority of computer and communication networks today rely on copper wiring to transmit data between nodes in the network. However, copper wiring has relatively limited bandwidth for carrying electrical signals which greatly constrains the amounts of data that it can be used to transmit.
Many computer and communication networks, including large parts of the Internet, are now being built using fiber optic cabling which has superior bandwidth capabilities and can be used to transmit much greater amounts of data. With fiber optic cabling, data is transmitted using optical or light signals (sometimes also called photonic signals) rather than with electrical signals. However, since computers use electrical signals as opposed to optical signals the light signals used to transmit data over fiber optic links must be translated to electrical signals and vice-versa during the optical communication process. Building such fiber optic networks therefore requires optoelectronic modules which mechanically and optically interface optical transmission mediums such as fiber optic cables to electronic computing and communications devices. Further, in order to provide the required bandwidth for high-speed communications multiple fiber optic elements must be used in networking equipment often referred to as xe2x80x9cparallel opticsxe2x80x9d systems for concurrently transmitting multiple signals over a single cable. The associated optoelectronic modules must therefore also be adapted for accommodating cables having multiple fibers which are presented for connection purposes in closely spaced arrays of fiber optic elements supported in special ferrules attached to the ends of the cables.
Signal conversion from electrical to optical and optical to electrical may be provided for through the use of corresponding arrays of semiconductor elements (photoactive components) which are deployed on semiconductor chips (optoelectronic devices). These photoactive components may typically be semiconductor devices such as photodiodes which act as photo-receivers or laser diodes which act as photo-transmitters. While modules using such devices can provide satisfactory signal conversion performance, the building of effective parallel optics subassemblies is a challenge. The optical and mechanical alignment of the photoactive components with the ends of the thread-like fiber optic elements must be precise for effective transfer of optical power. Since the fiber optic ends in parallel optics modules are closely spaced the complexity of this alignment task is further increased. Arrays of lenses are ordinarily positioned between the fiber ends and the photoactive devices for directing the photonic signals between them. The lens in these arrays need to be appropriately designed for efficiently collecting and focusing the light being transferred between the fibers and semiconductor components and need to be precisely aligned and positioned between the fibers and semiconductor components for effectively directing the photonic signals.
The present invention relates to lens arrays for use in fiber optic communications modules where multiple optical fibers are used for either transmitting or receiving optical signals. The lens array is adapted for optically interfacing a set of photoactive components such as semiconductor lasers or photo diodes deployed on an optoelectronic device (integrated circuit chip) with a set of optical communications fibers supported in an optical ferrule. The lens array is linearly deployed and is characterized by a fixed pitch or center-of-lens to center-of-lens distance which reflects the pitch of the fibers in the ferrule. The individual lens elements within the array are sized to have a greater lens diameter than the pitch distance and are accordingly laterally truncated at their boundaries with adjoining lens halfway between the lens centers. The lenses therefore have a greater height than lateral width. The increased height of the lens elements allows them to gather and transfer more light than would be the case with lenses having diameters which reflect the exact pitch of the fibers in the fiber array. The lens array is deployed as an integral part of a one piece lens and alignment frame. The lens and alignment frame includes a set of guide pins which are accurately positioned with respect to the lens array. The guide pins mate with corresponding alignment holes in the ferrule for precisely positioning the lenses with respect to the fibers in the ferrule. The fibers and lenses are in turn also precisely aligned with the photoactive components of the optoelectronic device (integrated circuit chip) which is attached to a carrier assembly onto which the lens and alignment frame is precisely mounted.